Many different options are available for power generation. The fuel can be combusted, gasified, pyrolyzed, bioprocessed or liquefied and utilized in engines, steam power plants (boiler, steam turbine, etc.), gas turbines, gas and steam power plants, and fuel cells. Among these, the most efficient and environmentally superior route for electric power generation is, of course, fuel cells. For the small-scale power (10 KWe to 5 MWe) sector, combined-cycle units are generally not applicable due to low efficiency and high cost. Such traditional steam power plants are generally less than 20% efficient. Engines are more efficient (20 to 40%), but are typically fired with diesel or natural gas. A more viable alternative to fuel cell technology in the near-term is a biopower system based on a gas turbine.
However, many conventional power plants based on biomass combustion have experienced operational difficulties, especially when firing non-wood biomass fuels. These problems resulted from the deposition of mineral matter on heat exchange surfaces (boiler tubes, superheaters and water walls) or from the agglomeration of ash in the fluidized bed. Gasification of biomass, in contrast, renders it possible to avoid these problems, minimize emissions and integrate with the fuel cell.
Currently, there exists many types of gasifiers, such as high pressure, low pressure, partial oxidation, autothermal, indirectly heated, oxygen/air/steam-blown, fixed/fluidized bed or entrained flow gasifiers. Each system has its advantages. For example, in direct gasification, partial oxidation or autothermal reactions are employed that yield an undesirable low-Btu fuel gas that requires oxygen input. The production of a low-Btu fuel gas is due to the fact that both exothermic and endothermic reactions take place in situ in the case of direct gasification, and the products of exothermic reactions dilute the product gases to be combusted for gas turbine power generation.
In view of the above, currently, a need exists for a new gasification process that is better suited for power generation applications.